Fathometer transducer unit



Dec. 27, 1955 J. MILLEN FATHOMETER TRANSDUCER UNIT Filed Nov. 12, 1952INVENT OR \JFMIE M/LLE/V,

ATTORNEYS United States PatentO 2,728,901 v FATHOMETER TRANSDUCER UNITJames Millen, Malden, Mass. Application November 12, 1952, Serial No.319,809 2 Claims. (Cl. 340-6) This invention relates to a method andmeans of facilitating the installation of fathometer transducers in thehulls of small vessels.

The transducer of the fathometer which may be a piezoelectrictransmitter-receiver element, has customarily been mounted on theexternal surface of the hull of a vessel with the leads running throughwater-tight glands provided in the hull. Such an installation, ofcourse, involves dry-docking of the vessel with attendant expense andinconvenience. It was subsequently found that reasonably satisfactoryperformance of the transducer can be obtained in wood hull vessels withsaid unit mounted inside the hull completely submerged in the bilgewater, where the thickness of the hull planking is not much in excess ofone inch. With no air space between the transmitter-receiver unit andthe water-soaked hull planking, the loss of energy transmitted to theoutside water will be reduced to a minimum. Where there is insufficientbilge water to permit complete submersion of the transducer, thepractice is to construct a well inside the hull of the vessel to receivethe unit. While this eliminates the necessity of drydocking, it isnevertheless costly and inconvenient, requiring the services of a shipscarpenter and tying up of the vessel.

It is an object of this invention to facilitate the installation of thetransducer of a fathometer on small wood planked vessels such as yachts,fishing boats and the like, whereby the installation may be accomplishedwithout tying up the vessel, without altering the hull, and withouthaving to employ the services of a craftsman.

Furthermore, it is an object of the invention to provide aself-contained transmitter-receiver unit containing the transducer whichis readily attached to the inside of the planking on the hull of a smallvessel.

Another object of the invention is to provide a method of installing thetransducer that may be practiced without having resort to anyspecialized equipment or to the services of a craftsman.

The invention is illustrated in a preferred embodiment in the drawings,wherein- Fig. 1 shows a perspective of the self-containedtransmitter-receiver unit for a fathometer;

Fig. 2 is a longitudinal sectional view of such unit taken on the line2-2 of Fig. l; and

Fig. 3 illustrates the mode of attaching the plastic diaphragm to thehousing.

The transmitter-receiver unit of this invention, containing thetransducer which may be of the piezoelectric type, comprises an openbottom outer housing 1, provided at the top with a suitably formedthreaded opening 2 and a screw cap 3 to seal the opening. Located ateach corner of the housing, and integral therewith, is an attaching lug4 with a screw-receiving bore for a purpose to be described. The housingis most conveniently molded or cast as a single piece with the screw capbeing attached thereafter. The housing may be made from a plasticmaterial that is adapted to be molded or cast. Such materials includeplastics of the acrylate, methacrylate,

2,728,901 Patented Dec. 27, 1955 formed with a laterally extendingflange 14 on the out: side thereof. The undersurface of the flanges andthe bottom ends of the side walls define a substantially planar surface.A thin plastic diaphragm 6 is attached to the underside of the housing 1in the aforementioned plane, thereby closing the housing at itsunderside. As will be apparent, the diaphragm 6 must make a waterproofseal 7 with the side walls and flanges on the housing. This 1 may beaccomplished as shown, in Fig. 3, by attaching the diaphragm to thehousing 1 with cement 15 that makes a waterproof joint.

" Plastic'cements are most satisfactory for securing the v diaphragm tothe housing, the cement being made es- 1 pecially for the particularplastics employed for the housing and the diaphragm. For example, with amolded styrene housing a toluol base cement may be employed. There areproper cements available for each of the well known plastic materialswhich result in practically a weld of the material and thus formextremely satisfactory watertight joints.

The diaphragm 6 is made from a thin plastic sheet material of filmthickness that is very flexible and readily conforms to an adjacentsurface upon being pressed thereagainst. For example, the diaphragm maybe cut from a polyethylene sheet that measures .002" to .010" inthickness. It is desirable that the diaphragm have ultrasonic wavetransmission characteristics very closely approximating those of seawater, but this is not absolutely necessary, the diaphragm being so thinthat its transmission characteristics are of little relative importance.An alternative arrangement of the diaphragm and the housing is to cementthe diaphragm to the inside wall of the housing. In this embodiment thediaphragm is made large enough so that it may be extended upwardly onthe inside walls of the housing and cemented at the top. This conrbutyrate groups and certain of the polyesters may be satisfactorily usedfor the diaphragm.

The transducer 7, which is illustrated as being of the piezoelectrictransmitter-receiver type, is suspended in the interior of the housing 1by brackets 8 depending from the top thereof. The brackets may besecured to the housing by rivets 9 or the like. Cable 10 carries theleads from the element 7 to conventional recording means. An opening isprovided in the side of the housing to admit the cable 10, the openingbeing made watertight by a gland 11.

In practice the housing 1 is attached to the planks 12 inside of thevessel by wood screws 5 passing through the bores of lugs 4, bringingthe diaphragm into intimate contact with the planking of the vessel. Thehousing is filled with either sea or fresh water through opening 2 andthe cap 3 is screwed shut to seal the unit. Thus the piezoelectrictransmitter-receiver element is completely submerged in the water, andthe weight of the water bearing on the very thin flexible diaphragm 6has the effect of pressing said diaphragm against the planking of thevessel and insuring the maintenance of the requisite surface-to-surfacecontact between the diaphragm and the planking.

The housing may alternatively be filled with castor oil or the like, theadvantage of this being to eliminate the possibility of corrosion of thetransducer 7 and the other parts within the housing 1.

In. p a io he ransduc 7 prod ces l ra-sank. waves which travel from thevessel through the Water and back to the vessel. Uninterruptedtransmission of thesignal is accomplished in the transducer unit of thisinvention. by. the provision of av path for the signal. that is ofsubstantially the 'sameimpedance as the sea water.

This path comprises the water or other fluid within thev housing invwhich the transducer is immersed, and the very thin flexible plastic,diaphragm 6, the latter having trans? mission characteristics closelyapproximating that of water. Neither does the planking of the vesselinterfere with the transmission of the signals, the wood possessing theinherent characteristic of consonance whereby it will respond to; thesignals.

The invention has been illustrated and described in. a preferredembodiment thereof, but may be practiced as well in other modificationswithin the scope thereof. It is therefore not intended that theinvention be limited except asset forth in the claims.

I. claim:

1. In a device of the class described, a substantially rigid housinghaving a transducer element carried there- 4. in. and secur d. to a. allthereofi. s idhQusinahe ns. dosed at the bottom by a thin and flexiblediaphragm sealingly engaging said housing so as to effect an integralleakproof unit therewith, and wherein said device may be placed on anon-planar surface with said diaphragm deforming into substantiallycomplete contiguity with said surface when said housing is, water filledto effect downward deforming pressure thereon.

2. A device as set forth in claim 1, wherein said diaphragm comprises apolyethylene sheet .002 to .010" in thickness.

References Cited in the file of this patent UNITED STATES PATENTS

